Manufacturers of corrugated paper products, known as Box Makers, produce both foldable boxes which have been folded and glued at the factory and die cut flat sheets which may be used either in their flat state or folded into desired shapes. These will be referred to as folded boxes and flat boxes respectively. The term “boxes” alone can refer to both folded and flat boxes. However, for the purposes of this patent application, boxes will refer to such before folding and gluing. Any reference to box length is understood to mean a distance in the material flow direction and any reference to box width is understood to mean a distance in a direction substantially perpendicular to the material flow direction.
Both the folded boxes and the flat boxes are produced by Converting machinery which processes the Corrugated Sheet Stock produced by the machinery known as a Corrugator. The Corrugated Sheet Stock is corrugated material cut to a specific rectangular size. However, the corrugated sheet stock has not been cut or notched to the detail typically required to produce the final foldable boxes or the flat boxes.
Often customized printing is required on boxes which may be done by 1) using a preprinted material integrated into the corrugated sheet stock on the Corrugator, 2) using flexographic printing during the Converting process or 3) applying ink or labels post Converting through various techniques.
During the Converting process the Corrugated Sheet Stock is transformed into a desired box configuration by performing additional cutting and optionally adding scoring and printing. There are multiple possible purposes for the additional cutting of the Corrugated Sheet Stock. Many of these cutting operations will result in pieces of the original Corrugated Sheet Stock being completely separated from the final box. These pieces are in general referred to as Scrap. The cutting can often result in notches within the box surface and along the edges. The result is that there are often variable width distances from cut edge to edge depending on where one measures the across the box in the cross flow direction.
In the conversion of the Corrugated Sheet Stock into Boxes the material is fed through machinery. The Lead Edge for both Corrugated Sheet Stock and Boxes refers to the first edge encountered as the stock or box travels downstream through the machine whereas the Trailing Edge refers to the last edge encountered as the stock or box travels downstream through the machine. The Corrugated Sheet Stock may be cut completely through in the cross-machine direction in one or more locations to create two or more boxes as counted in the through-machine direction. These are referred to as Ups. The Corrugated Sheet Stock may alternatively or additionally be cut completely apart in the through-machine direction in one or more locations to create two or more boxes in the cross-machine direction. These are referred to as Outs. (See briefly, FIGS. 38A-38B.)
There are multiple methods by which the cutting of the Corrugated Sheet Stock may be accomplished during the Converting process. One example method for cutting Corrugated Sheet Stock is known as Rotary Die Cutting. A typical configuration of a Rotary Die Cutter, known as Rule and Rubber, uses of a pair of cylinders where the lower cylinder, known as the Anvil, is covered in a firm rubber material and the top cylinder is mounted with a Die Board. The Die Board is normally a curved plywood base in which are embedded a customized set of steel Rules, which protrude from the plywood base and when rotated with the Anvil will cut and score the Corrugated Sheet Stock into the desired cut/scored box. An alternate configuration of the Rotary Die Cutter swaps the locations such that the Anvil is the top cylinder and the Die Board is mounted to the lower cylinder. The transportation speed of the box, as determined by the effective linear speed at the nip of the Die Board and Anvil, is known as Line Speed.
A Stacking Apparatus is positioned downstream of the Rotary Die Cutter to accept the cut/scored boxes and to ultimately form neat stacks of the cut/scored (and optionally printed on) boxes. If short stacks of individual Outs are produced, they are known as Bundles. If short stacks are output and the Outs are still connected with perforated cuts they are known as Logs. If taller stacks are output they are known as Full Stacks. These stacks, regardless of type, are referred to herein as Loads.
The Box Makers has both fixed and variable costs associated with running of their business. The number of boxes produced in a given time period determines the Average Production Rate. A higher Average Production Rate is desirable. There are multiple factors that can affect the Average Production Rate. The integral of the rotational speed of the Rotary Die Cutter and the amount of time Corrugated Sheet Stock is actually being fed through the machine, Feed Time, determines the Average Production Rate. Focusing on the Feed Time, there are four primary reasons sheets are not continuously being fed during operating hours. First is the time for maintenance or repairs required for the machinery. Second is setup time where the operators are changing from one order to another. Third is clearing of Jams. Forth is when operation of a Stacking Apparatus calls for creation of a gap in the flow of the boxes at a discharge end of the machinery that feeds the Stacking Apparatus in order to perform what is referred to as a Load Change Cycle. A Load Change Cycle is an operational phase when formation (e.g., stacking) of one Load is completed and must be discharged from the end of the Stacking Apparatus and when the formation (e.g., stacking) of a next Load is to be started. Creating such a gap in the flow of boxes entering the Stacking Apparatus can be done by interrupting the Feed Table for a length of time known as a Feed Interrupt Time. It would be desirable to not interrupt the Feed Table that feeds boxes (sheets) into the Stacking Apparatus. Having a Load Change Cycle that allows for Zero Feed Interrupt Time can desirably increase the Average Production Rate for the Box Maker.
The quality of the box surface and print quality at the output of the Stacking Apparatus are important factors to the Box Maker. There are two classes of Rotary Die Cutters, ones that print on the top surface and ones that print on the bottom surface. Care should be taken by the Stacking Apparatus during the Load Change Cycle to not Scuff (e.g., abrade) the printed or other fine surfaces of the Box.
The downstream processing units after the Rotary Die Cutter generally comprise four functional modules.
The first functional module at the receiving end of the post-Die Cutter apparatus is typically referred to as the Layboy Function. Its function is the receiving of the boxes from the Rotary Die Cutter and assisting in the removing of the scrap from the boxes. Often speed variations are implemented in this section in preparation for the second functional module.
The second functional module will be referred to as the Shingling Function. This is a widely used option in the post-Die Cutter processing and stacking operations where the boxes can be changed from Stream Mode to Shingle Mode. Stream Mode is where the boxes are being conveyed without overlap at higher speed. Shingle Mode happens with a transition to conveying means that are running slower than Line Speed and thus the boxes are caused to partially overlap one another and thus create what is known as shingle of boxes. The speed variations referred to in the Layboy Function may be higher than Line Speed to pull gaps between the boxes in order to allow the creation of the Shingle of boxes.
The third functional module after Die Cutting will be referred to as the Stacking Function. The boxes are now conveyed in either Stream Mode or Shingle Mode to where respective stacks of boxes are being created. One style is for the discharge end of a Stacking Conveyor to change in elevation in order to accommodate the growing stack of boxes such that the conveyed boxes are deposited on the top of a currently being formed stack. This is known as an Up Stacker which an example of can be seen in prior art U.S. Pat. No. 7,954,628. An alternative method is for the discharge end of the Stacking Conveyor to remain at a fixed elevation and the Stack Support Surface which is disposed under the growing stack of boxes moves down, again as more of the conveyed boxes are deposited on the top of the growing stack. This is known as a Down Stacker which an example of can be seen in prior art U.S. Pat. No. 5,026,249. An additional alternative is a combination where both of the discharge end of the Stacking Conveyor and the Stack Support Surface are changing respective elevations.
Up Stackers and Down Stackers both have advantages and challenges. Up Stackers have the advantage that it is more convenient for the operator to be able to walk onto a low level floor conveyor upon which the stack of the Up Stacker is being built, but it has the engineering challenge in that the angle of the deck of the Stacking Conveyor changes as the growing load is being created. Near the discharge end of a Straight Up Stacking Deck, (see briefly 33 of FIG. 2), the Linear Space in the horizontal direction under the pulleys at the discharge end of the deck becomes smaller as the incline angle of the Straight Up Stacking Deck increases. A Curve Down Stacking Deck as in FIG. 2 of U.S. Pat. No. 5,026,249, has substantial Linear Space under the pulleys near the discharge end, as do multitude of Straight Down Stacking Decks, as an example FIG. 3 of U.S. Pat. No. 4,359,218. Problems due to lack of substantial Linear Space for a Straight Up Stacking Deck may be seen in FIG. 4 of prior art U.S. Pat. No. 6,234,473. This lack of substantial Linear Space associated with Straight Up Stacking Decks along with inability to provide reliable operation at the maximum Rotary Die Cutter Speed is one of a number of problems that can be overcome by aspects of the present disclosure of invention.
When respective stacks are being formed by the boxes falling off the discharge end of the Stacking Conveyor and onto a vertical stacks accumulating region, there is a potential downside of having the Stacking Conveyor at a substantial downward angle when first starting a new stack. Depending on the cutouts required to make the box, when the consecutive sheets are pressured downward onto the top of the stack, the cutouts can catch on edges of previously stacked boxes and cause jams. As a result, and in accordance with one aspect of the present disclosure, a solution is provided of avoiding having a Stacking Deck operating without a substantial downward angle for its incoming boxes.
In order to perform the Load Change Cycle, the Shingle of Boxes should be selectively separated based on the order settings in order to get the correct count in each Load. The Box Maker and their customers expect the box count in the Loads to be consistently accurate, this being an aspect enabled by the present disclosure of invention.
The fourth functional module downstream of the Die Cutter will be referred to as the Hopper Function. This is an area where the full stack of boxes or bundles of boxes are formed by means stacking and it generally includes an Accumulation means and it performs part of the Load Change Cycle. The optimal Load Change Cycle is one that can operate at the maximum speed capabilities of the Rotary Die Cutter, can accumulate enough boxes to allow for the variable time it takes to discharge a completed Load from the Stacker, can handle both Stream Mode and Shingle Mode operations, can reliably split Loads between any of the Ups at an accurate count, does not Scuff (e.g., abrade) the printed or other fine surfaces of the boxes, makes a nicely tamped stack of boxes and does not necessarily call for a Feed Interrupt Time (thus enabling ZFI).
Some Stacking Apparatus require the individual boxes, Outs, to be separated laterally across the machine in order to output individual side by side Bundles or Full Stacks from the Hopper Function. This can be performed during the Layboy Function as describe by U.S. Pat. No. 3,860,232, the Singling Function or the Stacking Function as described by U.S. Pat. No. 5,026,249. In the Hopper Function, making a clean separation between these side by side Bundles or Full Stacks may be performed by the Stacking Apparatus both during the building of the stack and during the Load Change Cycle.